I want to say here's the fundamental problem : I'm looking at a dev board for, say, a TI/AD/Microchip microprocessor or DSP. This is long before a full product design; we're talking proof-of-concept work here. I want to send data from a PC to be processed by my firmware, or have my firmware send data to my PC. And I want the rate to be of the order of 1-10MB/s.

15+ years ago, 1-10MB/s would have been quite niche. kB/s would have been more usual, and the dev board would have had a DB9 connector on it. I could have just plugged a serial cable between the dev board and my PC, perhaps with a USB-to-serial converter, and read and write to COMX or /dev/ttySX.

However, this scheme has a number of limitations that are now starting to show up:

I want MB/s, not kB/s.The absolute max UART rate a 100MHz device could manage is still only 0.7 MB/s. SPI on the other hand allows up to 3-4 MB/s.It's incredibly rare for PCs to come with serial ports now, so specialised adaptors are needed to interface with a PC eg. USB to serial cable.But I'm stumped for what I could use to replace the old serial scheme. The main context for this question is sending serialised debugging data between vendor dev boards and a PC before design is finalised, so anything requiring secondary devices eg. Bluetooth isn't super useful. The µPs I typically work with are in the realm of TI's MSP430, Microchip's PIC32M*, and low power DSPs like the TI C55x or C674. Their dev boards might typically come with headers connected to SPI/I2C/UART peripherals.

Ethernet would require full implementation of a networking stack, which isn't really practical on the constrained DSPs or µPs I often work with. Furthermore most PCs only have one ethernet port, if at all, so you wouldn't be able to use it for wired networking.

Ground-up USB requires getting a vendor ID from a 3rd party, and reinventing all sorts of wheels at the driver and software level just to get data from one device to another.

Ideally I'd like to just be able to dump bytes in a peripheral register on my µP and drain it using Python on the PC or vice versa, using a cable most IT departments would have lying around, and get 1-10 MB/s. A bonus would be not having to poll every available port of whatever kind to find the device on a PC. Is this possible?All guys has any suggestions that welcome.Thanks all

A direct USB connection can get that kind of speeds. A High-Speed connection is 480Mbps overall or about 60MBps. Of course, that's shared by everything on the bus, and the kind of USB connection (Bulk, Interrupt, Isochronous, etc) defines the latency and smoothness of the transaction, but it's certainly possible to get high speeds like that.

I am working on a new USB stack for chipKIT which includes HS support for the MZ chips. It's not optimized yet for ultra high speed, but it works. It's all in my USB branch of the chipKIT-core:

https://github.com/majenkotech/chipKIT-Core/tree/usb

I can't remember the speeds I was getting in testing, but it's certainly a helluva lot faster than serial. And you have the choice of protocols - CDC/ACM, Raw HID, etc. (audio coming one day too, along with Mass Storage Device).

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Doesn't seem that hard unless you want to use stuff in the 'normal' way. i.e.- gotta do http. instead of just send the data.

The big advantage of USB2 was the receive buffering so the processor could be doing something else while waiting for data to come in. Most so called high speed data consists of ping-pong buffers. But if you don't have to do that much processing with the received data you can just dedicate your micro to mostly receiving or sending data.

In a lot of cases your really have bursts of data at the high rate followed by display or analysis. In this case your problem is not that hard. Conventional Oscilloscopes for example display at a high rate but only in bursts.

The next stage of the new USB stack is to implement DMA so as to free up the CPU a little more while reception/transmission is going on. That's going to be fun...

Especially on the MZ chips that have their own dedicated USB DMA channels...

_________________Why not visit my shop? http://majenko.co.uk/catalogUniversal IDE: http://uecide.org"I was trying to find out if it was possible to only eat one Jaffa Cake. I had to abandon the experiment because I ran out of Jaffa Cakes".

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